In recent years, advances in technology, as well as ever evolving tastes in style, have led to substantial changes in the design of automobiles. One of the changes involves the complexity, as well as the power usage, of the various electrical systems within automobiles, particularly alternative fuel vehicles, such as hybrid, electric, and fuel cell vehicles.
The power and/or torque density required for motors used in such vehicles is extremely high. The amount of power or torque that can be generated by a particular motor is limited in large part by the winding, or coil, temperature within the motor during operation. If the motor is permitted to operate such that the winding temperature becomes too high, the efficiency of the motor may be adversely affected, the permanent magnet within the motor may become demagnetized, and the internal solder joints within the motor may be irreversibly damaged.
One method commonly used to protect motors from overheating is to simply shut down the motor when the internal temperature of the motor reaches a preset limit. Another method is to limit the torque proportionally to the temperature difference between the present winding temperature and the temperature limit. However, neither of these methods allows a torque limit to be set analytically at various stages of operation, nor do they guarantee continuous operation of the motor.
Accordingly, it is desirable to provide a system and method for limiting the operating temperature of an electric motor that allows the operational temperature to be continuously controlled at various stages of operation. In addition, it is desirable to provide a system and method that facilitates continuous operation of the motor while limiting the operating temperature. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.